With the progress of the technology, the driving efficiency of the electronic device is raised up. For increasing the driving power, accelerating the driving speed, and conforming to the trend of miniaturization, the volume of the electronic device is reduced and the design of the inner structure is compacted. Therefore the circuit board of the electronic device, such as the power converter, is designed as a double-layer circuit board or multi-layer circuit board, and the electronic elements are placed on both sides of the circuit board for saving space.
Generally speaking, the electronic elements on the circuit board, such as capacitor, transistor, resistor, inductor, transformer, and diode, are high-power heat producing elements. Hence a lot of heat is produced on both sides of the circuit board while these electronic elements are working. The stability of the electronic device depends on the heat dissipating efficiency thereof; however, for satisfying the circuit layout in a finite space, the space for disposing the heat dissipating structure is limited.
Take the power converter for example; with the improvement of the semiconductor and packaging technology and the mass usage of high frequency switch, the power conversion efficiency and the driving efficiency of the power converter are both raised up than ever. Nevertheless, if the heat produced by the high-power electronic elements on both sides of the circuit board cannot be dissipated efficiently, the function and the lifespan of the power converter will be seriously affected. Furthermore, the overheated power converter might become out of order. For dealing with the problem, the heat sink is used to assist heat dissipation.
However, as the foregoing descriptions, with the trend of miniaturization of the electronic device, the space reserved for the heat sink is limited; hence the heat sink can be disposed only on one side of the double-layer circuit board or multi-layer circuit board of the power converter. When the power converter is assembled on the system circuit board of the electronic system or fixed on other object, an air gap is formed between the side of the circuit board without the heat sink and the system circuit board (or the object). It is to be understood that the heat dissipation is hindered because of the air gap; therefore the electronic elements on the circuit board might be damaged owing to the heat accumulation. The damaged electronic elements may affect the stability of the power converter and further cause the shutdown of the electronic system. Moreover, no matter the active or passive cooling method is used in the electronic system, the heat accumulated in the air gap cannot be dissipated actively because the space for air flow is limited and thus a dead space for heat dissipation is formed.
Therefore, it is necessary to develop an electronic device with dual heat dissipating structures to dissipate the heat from both sides of the double or multi layer circuit board efficiently in a limited space for dealing with the foregoing defects.